1989 Mercury 70hp Reputation

[NJCoastFlyFish]

I know this is the wrong forum to throw this in with all the Merc Fanatics, but i'm sceptical when it comes to mercury engines, here is the one I am looking at this weekend maybe someone can ease my fears.<br /><br />Engine is a 1989 mercury 70hp, been used in freshwater all it's life. Guy said he can show me how it runs (supposedly great) and of course i will check compression and all that. Do these engines have the bulletproof rep like the evinrude 70's or are they anchors? I don't see a lot of them still around, that is another reason I am weary, but the price seems good.<br /><br />I get engine, prop, and controls for $700<br /><br />What do you all think? was 89 a good year?

 

[WillyBWright]

Re: 1989 Mercury 70hp Reputation

Too much $$$. They like to eat pistons. Make sure the max timing is OK and never use stale gas. One good feature may be the power trim/tilt. They were using the same unit as the V-6s. Make sure the water pump is fresh. The rubber impellers can break vanes when they get old. Then you cook the motor. They aren't one of Merc's more sought-after older motors mostly because of the piston-eating problem.

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

This one doesn't have tilt and trim unfortunately, but I can probably find one for easy enough...<br /><br />Eat pistons, that doesn't sound good at all, why are these known for eating pistons? How much would a repair be if I had to replace the pistons next year, $1000? $2000? What if I already had a junker motor with decent pistons sitting around, is that something I can do myself given the time and literature...<br /><br />And what is the max timing?

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

He also has pretty much the same engine but a 50hp, also freshwater use and $100 less, would this be a more reliable engine than the 70hp?

 

[WillyBWright]

Re: 1989 Mercury 70hp Reputation

The inline-4 50Hps are one of the best Mercs ever made. The 3-cylinder 50s were a detuned version of the 70 and somewhat less prone to eat pistons, but they're kinda rare. There are gazillions of the 4-cylinder 50Hp Mercs still running strong in various incarnations.<br /><br />They eat pistons from detonation. They're real touchy with the maximum timing advance and gas that has lost octane. Either/both eat the pistons. I like to retard the maximum throttle timing by 2 degrees from spec just to be safe. 2 degrees too advaced causes detonation. 2 degrees retarded and you'll never notice any loss of speed or power. It's pretty tiny and it can save your pistons from a stale tank of gas. <br /><br />Those may also have something called Autoblend which is an oil injection system that has a bad reputation and few replacable parts. If you have one of those, you're better off mixing your gas by hand.<br /><br />Overhauling those without the weird piston ring compressors they need is possible, but really difficult and damned frustrating. The piston/rod/crankshaft assembly has to be dropped into the block. You have to get it all to drop together in sequence without getting the crankshaft crooked. First timers usually break rings.

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

So if I retard the timing I should be ok with this engine? And always use fresh gas? Maybe even throw a gallon of higher octane gas or some of that octane boost stuff they sell in auto zone (maybe that is going to far)<br /><br />These all seem like problems I can control, and the oil delivery is no problem, I can take that out and do it the old fashioned way. I just need something that works and isn't going to leave me in the middle of the ocean, so if the timing is under control and the octane is all peachy, is this thing still gonna blow, should I steer clear or just go for it, take my chances like with any other old outboard

 

[emckelvy]

Re: 1989 Mercury 70hp Reputation

Are you sure you're talking about the right motor? Isn't the '89 one of the Big Three family that was rated 70, 80, and 90 HP??? <br /><br />The old 3-cyl Merc (650/700) that was basically 3/4 of an 850-4 was very highly-stressed and prone to burning up but I don't believe the Big-Inch version would be the same. Completely different design. The 70 HP would be the lowest-stressed version of the three.<br /><br />I guess if we had a serial # we could pin it down as to what C.I. motor this is.......ed

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

I just double checked, nada.com says in 89 mercury made these in three cylinder - 50, 60, 70, 80, 90 the 100 was a four cylinder they also made a 45 four cylinder then the 35 was a two cylinder.

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

Also, Nada says the average retail of this engine should be $850, so I think i'm getting a good deal since I will also be getting controls and prop, but that is if I decide to get her. The seller also wasn't firm with the asking price so i'm thinking maybe $600, but again, I need some more info on this engine

 

[inlineal]

Re: 1989 Mercury 70hp Reputation

Ed Mc.....Sounds like we live pretty close to each other..Like Mercs huh.??...WE should get together sometime........Serial #...a must....whos saying this 70 HP is really of that year...I just sold parts to a fellow who was told his motor was a 1986...Turns out it was a 1970.!!!...Mercury Marine revamped all production in 1988 ..1989...The new three cylinder HP of 70..75..80..90.. are made from V-6 parts...I call them the "Big Bore"..three cylinder...Almost indestructable...Have been running into problems with the stators on some..Mercury wants some with 9 amp stators changed to 15 amp...Makes a big difference in running...We use CDI parts as much as possible...Its nice to find a service manager at a Mercury franchised shop that is willing to go through service bulletions of your motor for updates...Al...

 

[JB]

Re: 1989 Mercury 70hp Reputation

If you know this is the wrong forum, why did you post it here?<br /><br />Moving to non-repair.

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

JB-I figured it should be in a merc based forum but it would get biased results there, hence "maybe this isn't the right forum" I just want to get some background on the engine <br /><br />I will get the serial number tonight-

 

[orca]

Re: 1989 Mercury 70hp Reputation

Easiest way to check which model you have.<br />Remove the cover, count the carbys. If you motor is 3 Cyl & 3 Carbys then it is the later model, great motor and almost unburstable.<br />If however the motor is 3 cylinders and 2 carbys then it is the older model, this is the motor that needs to have the timing retarded to stop pistons melting.

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

Thanks whaley, I guess I was confused, I thought the newer models were the ones with the timing issue and the older ones were more reliable, guess I mixed it all up, good to know it is almost unburstable thanks for the help

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

Alrighty the serial is 5354082 and he said he thinks it has three carbs. Right now it is between this engine and an evninrude 70 hp with 100psi on all thee cylinders (kind of on the edge), the evinrude is two years older than this though and doesn't include controls, the seller also has problems keeping in touch, decisions decisions

 

[NJCoastFlyFish]

Re: 1989 Mercury 70hp Reputation

Wait, I just checked on a couple mercury sites and unless i'm mistaken, this serial number would actually put this engine around 1979, someone correct me if i'm wrong? I talked to the guy and he said 89, and on the listing he put it also says 89, looks like more time wasted searching for an ouboard, good thing I asked for the serial number before I drove all the way to albany!

 

[joblo33]

Re: 1989 Mercury 70hp Reputation

Yup, that's a '79.<br />Eric

 

[phatmanmike]

Re: 1989 Mercury 70hp Reputation

jb is getting touchy. ouch